How do I easily gain weight I am 20 pounds underweight even though I am constantly eating and when I don't for a long period of time or don't eat enough I get dizzy, I have a headache, and feeling like I am about to faint. I weigh 85 pounds right know even

I . I am concerned to hear that you get dizzy, feel like you will faint and get headaches. If you have not been to your doctor, please see your doctor. Your doctor will do a physical evaluation and check things like your blood sugar and your thyroid level. Don't know if you menstruate or if you have a past history of any eating disorders. The best thing to do is ask your parents to see your physician to have this properly assessed.